Also have an M50d F15, picked it up a few months for a song.
Have got it remapped by Pramod Parag. Night and day would apply if it wasnt for having all of the go to start with. have done the start stop mod, and remapped the trans at the same.
i also have brought an aftermarket transmission pan that is alloy, accomodates an aux temp sensor, and an extra 1.5L of oil. Although the cooler is thermostat controlled, it will decrease the amount they rise if doing a pull up hill with 3 tonnes of trailer on the back, which is what they are made for!
also replaced the front grills and mirror caps for black ones, the silver looks naff, like youve got mirrors from another car or something
Only thing i dont like about it is the interior colour is tan, which is hard to keep clean with my lifestyle. I prefer black, but ill just have to get used to cleaning the inside more regularly!
happy motoring